What is an electronic shutter?

Started Nov 26, 2014 | Discussions thread
Chas Tennis Contributing Member • Posts: 920
electronic shutters, mechanical shutters, Jello Effect

During the following discussion of timing considerations, each elemental detector of the sensor is still always exposed for the set shutter speed.

Electronic Readout & Jello Effect Distortions. Most current cameras use CMOS sensors. CMOS sensors readout using a scanning process known as 'rolling shutter'. Rolling shutter reads out one line of the sensor's elemental detectors at a time. This results in parts of the frame being readout out at different times than other parts. For example, the top of the frame may be readout at a time earlier than the bottom of the frame. When objects are moving during the scanning process the rolling shutter delay causes an image distortion named 'Jello Effect' distortion.

Mechanical Shutters - Focal-Plane and Leaf. Most DSLRs have a focal-plane mechanical shutter. Some smaller compact cameras have a mechanical leaf shutter. Some cameras have no mechanical shutter and use only the electronic shutter.

The mechanical shutters are used to avoid electronic Jello Effect distortion. However, a very similar distortion still exists for a mechanical focal-plane shutter but the mechanical focal plane shutter scans across the sensor faster than the electronic rolling shutter readout of most CMOS DSLR cameras. Therefore, the mechanical focal-plane shutters produce less distortion than the rolling shutter's Jello Effect.


Leaf shutters expose the entire sensor at the same time so there is no delay in various areas of the frame. No Jello Effect distortion and no distortion as from the slow scan of the focal-plane mechanical shutter. There's still motion blur from the shutter speed. See test below.

To test Jello Effect distortions I viewed a rotating straight bar on a disc. The Casio FH100 camera has a leaf shutter and it does not distort in the same way as a mechanical focal plane shutter. Testing was for burst modes both with and without a mechanical leaf shutter. Maximum frame rate specs: electronic shutter 40 fps, leaf shutter 10 fps. The focal leaf shutter has a slower frame rate in burst mode but has less distortion.


Chas Tennis

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